Increased levels of antiviral MxA protein in peripheral blood of patients with a chronic disease of unknown etiology

Interferon alpha (IFN-alpha) is synthesized in response to viral infections . MxA protein, induced specifically by IFN-alpha and beta, expressed in per ipheral blood cells, is detected more consistently than circulating IFN-oc in serum of patients with viral infections. Thus, activation of the IFN-alp ha /MxA system can be used as additional marker of the presence of a virus in patients. Therefore MxA protein and IFN-alpha levels were measured in pa tients with multiple sclerosis (MS), a chronic neurological disease of unkn own etiology, in order to investigate the possible role of viruses in the e xpression of this disease. The means of MxA values obtained by using an imm unochemiluminescent assay were significantly higher in blood of patients wi th remitting (n = 197) or relapsing (n = 39) multiple sclerosis (MS) patien ts and in patients with viral infections than in blood from healthy control s (n = 25) and from patients with bacterial infections (n = 12). Intra-indi vidual variance in MxA levels in seven clinically stable remitting patients with MS was observed in the course of a follow-up, and high MxA levels wer e detected in three of them in blood samples collected consecutively over s everal months. By using an ultra sensitive assay, a higher MxA-inducer acti vity was obtained with sera from MS patients (n = 39) than with those from healthy controls (n = 12). Experiments wit neutralizing antibodies proved t hat this activity in serum from patients was due to IFN-alpha, whereas IFN- alpha could not be detected by other methods. Altogether these results demo nstrate that there is an activation of the IFN-alpha /MxA system in MS pati ents, which is consistent with the hypothesis that a viral infection may be associated with MS. (C) 2001 Wiley-Liss, Inc.